1. Field of the Invention
The present invention relates an apparatus and method of operating a chromatography column and, more particularly, to such a chromatography column and the method for performing maintenance, such as changing resin retention screens within the chromatography column without requiring the use of a crane to disassemble the column.
2. Description of Related Art
Chromatography is a process of separating the components of a mixture of chemical substances through the percolation of fluid through a body or bed of comminuted or porous rigid material, known as media. In the process, the various component are often resolved, or separated, by their selective retardation as they are transported through the bed by a moving fluid or buffer. A solution of the substances to be separated becomes the moving phase of the system passing through the interstices in the stationary or continuous phase which are finely divided particles, possibly in the form of a gel slurry.
The substances in the moving phase are poured into the top of a chromatography column filled with the finely divided material, i.e., the media, that can absorb differentially the substances to be separated. The particular material used for the media varies widely with the substances to be separated. As the solution percolates down the column the components are separated from the buffer fluid which generally is pumped back into the top of the column so as to again pass down through the bed as a carrier. The different substances as they travel down the column at different rates form bands of the different substances which are individually collected at the outlet.
A chromatography column typically comprises a hollow vertically disposed cylindrical housing including a liquid dispensing section at the upper end and through which the buffer and substances to be separated are dispensed to the media bed, and a liquid collecting section at the lower end for collecting the substances and buffer individually. The media or bed through which the buffer fluid and mixture to be separated and purified percolates is located between these sections. The liquid dispensing section and liquid collecting section may each include a respective distribution plate and at least one of the plates may be connected in an assembly with an axially movable plunger-like body positioned within the housing. After the column is charged with the bed media, the plunger body may be forced toward the bottom to compress or pressurize the media bed which has been poured into the column. Alternatively, a fixed bed media may compress the media bed.
Chromatography columns typically require periodic maintenance and inspection within the column. Prior art designs have allowed for the plunger to be moved with hydraulics to about two inches or less above the top of the cylinder to allow visual inspection within the column. No prior art designs are known to exist which allowed the plunger to be lifted high enough to perform maintenance on the interior portion of the plunger or within the cylinder. Such maintenance includes the replacement of a resin retention screen which normally allows fluid to flow through orifices typically on the order of about ten microns while preventing resin from leaving the column. The screens are held to the plunger with connectors and an inner clamp nut. In the prior art, the plunger had to be completely removed from the cylinder with a crane in order to replace the screen and/or work on the distributor plate since the plunger could only be lifted about two inches or less above the cylinder which did not provide enough clearance for a mechanic to access the connectors or inner clamp nut to disconnect and replace the screen.
A second screen and plate is typically located at the bottom of the cylinder on a base. In many circumstances, the bottom of the cylinder assists in holding the screen in place against the base so that it cannot be removed from within the cylinder upwards without first removing the cylinder relative to the base. Additionally connectors and an inner clamp nut also assist in retaining the bottom screen in place. In the prior art, the cylinder had to be disconnected from the bottom and lifted with a crane from the bottom. The bottom screen could then be replaced in a similar fashion as the top screen.
Many chromatography columns are located in clean rooms. Often the solutions utilized may be highly flammable, such as tolulene or acetate. Few cranes have been devised which can meet the requirements of a clean room. Additionally, the cost of a specially designed crane is believed to be very expensive. Furthermore, it is likely that the clean room would need to be designed around both the crane as well as the column for maintenance purposes. This would require higher ceilings and supports. Many column users avoid the problems of having a crane in a clean room by moving the columns from the clean room to another room for maintenance. Once the columns have been moved, they have to undergo a cleaning or verification procedure to be allowed back into the clean room. This is believed to be time consuming and tedious work.
Accordingly, a need exists to improve the maintenance methods by providing an improved chromatography column.
The present invention recognizes and addresses these needs and others.
Consequently, it is an object of the present invention to provide a chromatography column capable of lifting the plunger to a sufficient height above the cylinder to allow access to the lower surface of the plunger for maintenance.
It is another object of the present invention to provide a chromatography column capable of lifting the cylinder above the base to allow access to the bottom of the column, as well as access the bottom of the cylinder, in a preferred embodiment.
Accordingly, the present invention provides a chromatography column having a cylinder defining a cavity for containing media therein. A plunger, or piston, is operatively coupled to a hydraulic piston moveable through at least a portion of the cavity within the cylinder during operation. A base is normally connected to the cylinder. The plunger may be operatively coupled to the hydraulic piston to adjust the height of the plunger above the base to provide a desired resin height between the plunger and the base for operation. The plunger may also be utilized to exert a force on the resin to xe2x80x9cpackxe2x80x9d the resin in the column.
During maintenance, the plunger may be lifted with a drive system such as one including a first hydraulic piston. The plunger is lifted a distance sufficient to allow access to perform maintenance on the bottom surface of the piston, such as to replace a screen. This distance is preferably at least six inches and more preferably about twelve inches. With the plunger in a raised position, safety rods may be positioned to ensure that the plunger will not drop should a hydraulic failure occur. After performing the maintenance, the safety rods may be removed, and the plunger lowered.
During a second maintenance procedure, the hydraulic system is configured to lift the cylinder by removing bolts which normally retain the cylinder against the base of the column. The hydraulic system may then lift the cylinder a second distance above the base to allow maintenance, such as replacement of a screen proximate to the base. Safety rods may be used between the cylinder and base during the maintenance. With the maintenance performed, the cylinder may be lowered and reconnected to the base.
The hydraulic system preferably includes a piston which is driven by a hydraulic cylinder. In the preferred embodiment, a plurality of hydraulic cylinders are utilized which are driven from a common hydraulic pressure source which is coupled to a controller. Upon receipt of a signal from a controller, the hydraulic cylinder(s) drive the hydraulic piston(s). Depending upon the configuration of the column, the piston(s) drive the plunger and/or the cylinder upwardly or downwardly.